Sifter of the circulating air type



S. SCHAUER SIFTER OF THE CIRCULATING AIR TYPE Nov. 4, 1969 5 Sheets-Sheet 1 Filed Dec. 27, 1967 Imam r0? Nov. 4, 1969 s. SCHAUER SIFTER OF THE CIRCULATING AIR TYPE 5 Sheets-Sheet 2 Filed Dec. 2'7. 196'? VE/PT/CAALY 4040574645 1969 s. SCHAUER SIFTER OF THE CIRCULATING AIR TYPE 5 Sheets-Sheet 3 Filed Dec. 2'7, 196'? NOV 4, 1969 5, SCHAUER 3,476,244

SIFTER OF THE CIRCULATING AIR TYPE Filed Dec. 27, 1967 5 Sheets-Sheet 4 WMZW Aqr

Nov. 4, 1969 s. SCHAUER 3,476,244

SIFTER OF THE CIRCULATING AIR TYPE Filed Dec. 27, 1967 5 Sheets-Sheet 5 lim United States Patent 3,476,244 SIFTER OF THE CTRCULATING AIR TYPE Siegfried Schauer, Hohenecken, Germany, assignor to Gebr. Pfeiffer Barbarossawerke AG, Kaiserslautel'n, Pfalz, Germany Filed Dec. 27, 1967, Ser. No. 693,907 Claims priority, application Ggrmany, Dec. 29, 1966,

Int. (:1. B04c 5/107 U.S. Cl. 209-133 7 Claims ABSTRACT on THE DISCLOSURE Background of the invention The invention relates to sitters for grit or the like. More in particular the invention is concerned with vertical sitters of the circulating air type where a cyclone is coaxially arranged with respect to the upper covered sifting housing for separating the fine components of the material being sifted, a sitting wheel disposed above the entrance of the cyclone and an annular space defined between the walls of the cyclone and the sitting housing for the coarse particles of the sittings.

The conventional feeding of the sift material takes place approximately centrally from the top of the sitter onto a dispersing disk which rotates rather rapidly and thus casts the sift material outwardly whereby it arrives in the current of circulating air.

It has been found that the outward casting of the sift material causes a relatively rapid wear of these parts of the walls of the sifter which are exposed to the impingement of the material. This results in relatively frequent repairs or replacement work for which the sitter has to be dismantled, particularly at its upper part.

Accordingly, it is an object of the invention to provide a possibility for. feeding the material into the sitter which eliminates these shortcomings, While the feeding of the sift material into the air current remains at least as good as before or is even improved.

In accordance with the invention this problem is solved in a circulating air sitter of the type described in that in the upper part of the sitting housing or chamber proximate the wall thereof and above the sitting wheel a circulating dispersing ring having a rectangular cross section is arranged which has a horizontal annular leg, and above this leg a stationary scraper of spiral shape is disposed, which scraper spiral begins where the inlet or feed sleeve for the sift material leads in above the horizontal annular leg laterally of the vertical leg of the dispersing ring and extends over the entire annular surface of the horizontal leg to its free border at the fed sleeve.

Summary of the invention As a result of the rotation of the dispersing ring the spiral progressively pushes the continuously supplied sift material along the entire circular path to the free edge of this ring. The material forms a curtain of sprinkled material from the inner border of the dispersing ring 3,476,244 Patented Nov. 4, 1969 downwardly, evenly distributed over the entire circumference of the dispersing ring and therefore of the sifter, and thus arrives in the current of circulating air.

The dispersing ring may be journalled on several rollers spaced from one another, at least one of which serves as the driver, preferably by taking advantage of the available friction.

The spiral of the scraper may begin outwardly of the feed sleeve for the material and may meet at the free inner border of the annular surface of the horizontal leg of the dispersing ring at the feed sleeve.

With this form of construction, it is advantageous to provide in the area below the dispersing ring, where the curtain of the spray move downwardly, a conical outwardly inclined ring, the level of which is adjustable, whose outer diameter is slightly larger than the inner diameter of the dispersing ring that produces the spray curtain and which is also larger than the greatest diameter of the cyclone.

By suitable adjustment of the level or height of the conical ring, between the dispersing ring and the upper edge of the cyclone, the border between the fine and coarse particles of the sitting material can be displaced so that, for example, not all of the fine material is sifted out but a part thereof remains in the coarse material as is frequently desired in practice.

However, the spiral of the scraper may also begin on the inside proximate the material feed sleeve and gradually widen toward the free outer border of the annular surface of the horizontal leg of the dispersing ring. This requires, of course, that the vertical leg of the rectangular cross-section of the dispersing ring is provided on the inside.

Starting preferably with this form of construction it is possible to provide in the lower region of the annular space between the center cyclone and the outer housing of the sifter a discharge ring having a scraper for the coarse material in a manner known per se. This leads to a decrease in the structural height of the sitter because the discharge of the coarse particles of the sift material results not along due to the effect of gravity, but also by the use of the aforementioned technical means. With the embodiment in accordance with the invention having an upper dispersing ring, the advantage is obtained here, that the discharge ring may in its mechanical form be constructed identically with that of the dispersing ring which serves as a discharge ring.

At the lower end of the intermediate wall forming the border wall of the sitting chamber between the outer annular space for the downward conduction of the circulating air current and the annular space proximate the inner cyclone for the coarse material and for the upward conduction of the air current, it is possible with the embodiment of the sifter described, to provide louvres directly above the discharge ring for the passage of the circulating air current.

Brief description of the drawings Further features and advantages of the invention will become apparent from the following description of the embodiments illustrated in the drawings in which:

FIG. 1 is a vertical section of a sitter where the conical ring is illustrated in a lowered position;

FIG. 2 illustrates the area between the dispersing ring and the inner cyclone with the conical ring drawn to a larger scale;

FIG. 3 shows a vertical cross-section of a sitter where the conical ring is illustrated in raised position;

FIG. 4 shows the region between the dispersing ring and the inner cyclone with the conical ring to an enlarged scale;

FIG. 5 is a plan view of the dispersing ring in accordance with FIGS. 1 and 3;

FIG. 6 is a section through the dispersing ring in accordance with FIG. 5 along the line A;

FIG. 7 is a section along line B in FIG. 5;

FIG. 8 is a sitter having a receiving and discharge ring;

FIG. 9 is a plan viewof the receiving ring from the outer border of which the sift material drops down;

FIG. 10 is a section through the receiving ring in a cordance with FIG. 9 taken along line A thereof;

FIG. 11 is a section along line B of FIG. 9;

FIG. 12 is a plan view of the discharge ring;

FIG. 13 is a section through the discharge ring taken along line A in FIG. 12 and FIG. 14 is a section taken along line B in FIG. 12.

Description of preferred embodiment The sifter has a central cyclone separator housing 1 for separating the sift material. A sifting wheel 2 rotates housing for producing the circulating air current which flows downwardly into the annular space between the outer housing wall 4 and the inner housing wall 5 of the sifter, is turned inwardly at the lower end of the housing 5 and again flows upwardly in the annular space between this inner housing and the cyclone separator housing.

The receiving of the sift material now no longer takes place centrally by way of a spraying disk but by way of a spraying ring 6 which is supplied with the material by an intake or feed sleeve 7. In the space defined by the L-shaped profile of the spraying ring 6, a stationary spiral 8 is disposed which, beginning proximate the intake 7, narrows from the outside toward the inner edge of the dispersing ring 6 while returning to the location of the intake 7.

The dispersing ring 6 rotates slowly so that the sift material discharged on it from the intake 7 is slowly pushed inwardly by spiral 8, whereby an evenly distributed spray curtain of the sift material is formed ove rthe entire inner circumference of the spray ring 6, and thus also over the circumference of the cyclone. This spray curtain then reaches the space 9 in the upwardly flowing air current whereby a pre-sifting of the material takes place already before it arrives in the area of the sifting wheel 2.

This spraying ring on the one hand affords the advantage that Wall parts of the sifter are no longer exposed to rapidly impinging particles of the sift material, thus eliminating, of course, the rapid wear of these wall parts. Furthermore, all parts of the sift material no longer reach the region of the sifting wheel, the largest particles drop down immediately into the annular space between the inner wall 5 and the cyclone 1. Only the remaining particles of the sift material are carried along by the air current and are conducted to the sifting wheel which rotates more or less rapidly, and which is in the form of a radial wheel and thus supports the air current. Here the main sifting takes place and in such manner that the particles of the material to be separated follow the air current and pass axially through the sifting wheel 2 while the coarser particles, due to the centrifugal forces to which they are subjected by the sifting wheel, are not able to follow the air current and are cast into the shaft for the coarse material. Thus, for a pre-determined grainsize corresponding to a pre-set sifting wheel velocity the sifting wheel provides a balance between the centrifugal force effected by it and the suction of the air circulated by the blower wheel.

The sifting action can be further improved, especially the composition of the different separated grain sizes, i.e. the borderline between fine and coarse material can be changed if as proposed in accordance with the invention a conical ring 10 is provided in the space 9 which is adjustable in height. This conical ring 10 has an outer diameter which is somewhat greater than the inner diameter of the dispersing ring 6. If the conical ring is in the upper position as shown, for example in FIG. 3, then a part of the fine components of the sift material remains in the coarse material. If the conical ring 10 is moved downwardly as shown in FIG. 1, then all of the line material is separated and collected in themcentral cyclone. Depending on the level or height of the conical ring, any desired displacement of thelimit between the two separated parts is possible as shown particularly in FIGS;2 and 4.

The journalling and drive ofthe dispersing ring takes place preferably by way'of rollers 11. Generally, it is sufiicient when one roller is driven and the driving force is transmitted by friction onto the dispersing ring 6.

FIGS. 57 illustrate particularly the relationship of the rotating dispersing ring and the stationary spiral 8. The direction of rotation of the dispersing ring is indicated by the arrow 12 in FIG. 3. i

In order to make possible the shortening of the heigh of the sifter, it is also possible in accordance with the invention to provide a discharge ring 13 in the lower-area which structurally is formed identically as the receivingdispersing ring 6. It is immaterial whether the receivingdispersing ring 6 discharges the siftmaterial inwardly or outwardly. If it discharges it outwardly as illustrated in FIG. 8, the ring 13 rotating in the direction 12 can be used which is journalled on rollers 11, at least one of which serves as the drive ring. Then, merely a scraper 14 is vrequired in the area of the outlet 15 in order to scrape the coarse material from the ring 13. For conducting the circulating air current, louvres are provided in the lower region of the inner wall Sproximate the discharge ring 13.

Having now described my invention with reference to the embodiments illustrated in the drawings I do not wish to be limitedthereto but what I desire to protect by Let'- ters Patent of the United States is set forth in the accompanying claims.

I claim:

1. Sifter of the circulating air type disposed about a vertical axis, comprising a covered sifting housing, a cyclone separator housing for separating. the fine components of the sift material, a sifting wheel arranged above said cyclone separator housing, said cyclone separator housing being coaxial withsaid sifting housing and having an upper entrance opening, an air circulator in the upper part of saidsifting housing, said sifting. housing having an outer wall and an inner wall disposed ,between said outer wall and said cyclone separator housing, said inner wall and the wall of said cyclone separator housing defining an annular space'for the coarse particles of the sift material, a dispersing ring rotatably disposed above said sifting wheel in the upperpart of said sifting housing proximatesaid inner wall, said dispersing ring having an L-shaped cross section with a horizontally disposed leg portion presenting a free edge, and a stationary scraper defining a spiral disposedabove said leg portion, a material feed sleeve extending into said housing toward said leg portion, said scraper spiral having one end fixedly secured proximate one side of said sleeve and extending along and above the annular surface of the leg portion of said dispersing ring to said free edge of said leg portion proximate the other side of said sleeve.

2. Sifter in accordance with claim 1, comprising a plurality of supporting rollers rotatably mounted below said dispersing ring to support said ring for rotation thereon, and at least one of said rollers being a driving roller.

3. Sifter in. accordance with claim 2, where said scraper spiral begins inwardly of said sleeve and increases in radius outwardly to said free edge of said horizontal leg portion to a position proximate andoutwardly of said sleeve.

4. Sifter in accordance with claim 3 comprising a discharge ring disposed in the annular space between said cyclone separator housing and the outer housing of said sitter, a scraper for coarse particles disposed above said discharge ring, said discharge ring being of L-shaped cross section with a horizontally disposed leg portion presenting a free edge.

5. Sifter in accordance with claim 4 including a plurality of louvres disposed at the lower end of said inner wall between the outer annular space of said sifter and the annular space proximate said cyclone separator housing and above said discharge ring.

6. Sifter in accordance With claim 1, where said scraper spiral begins outwardly of said sleeve and decreases in radius inwardly to said free edge of said horizontal leg 15 is greater than the inner diameter of said dispersing ring and also greater than the largest diameter of said cyclone separator housing.

References Cited UNITED STATES PATENTS 2,966,265 12/1960 Jager 209139 3,042,202 7/ 1962 Work 209144 3,237,766 3/1966 Humphreys 209139 3,275,140 9/1966 Rasmussen 209-139 3,308,949 3/ 1967 Schauer 209139 XR FOREIGN PATENTS 114,442 12/ 1941 Australia.

16,330 1906 Great Britain.

FRANK W. LUTIER, Primary Examiner U.S. Cl. X.R. 

